1. Field of the Invention
The present invention relates to a novel aluminum brazing alloy which helps increase the strength of a solidified structure in brazed joint portions formed by brazing, and which also helps increase the strength against high pressure.
2. Background of the Prior Art
In recent years, plate fin type heat exchangers brazed with an aluminum alloy to exhibit resistance against high pressure have been widely used, for example, in the treatment of natural gases and the development of heat exchangers having superior high pressure resistance, particularly at the fin joints, has continued.
To date, brazing material used for aluminum alloy brazed plate fin type heat exchangers has generally been composed of an Al-Si type alloy when it is to be brazed with flux, or is composed of an Al-Si-Mg type alloy when it is to be brazed without flux. However, the joint formed by using such brazing materials provides a solidified structure which includes a eutectic structure, and is brittle. In particular, when a brazing material of the Al-Si-Mg type is used or when the base metal contains magnesium, the brazed joint exhibits a marked loss of strength.
Study has so far been concentrated on reinforcement of the brazed joints. In the case of a plate-fin type heat exchanger, however, limitation on such improvements are imposed depending upon the shapes of fins, amount brazing materials supplied and properties of the brazing material. With the high-pressure plate-fin type heat exchanger which requires a high joint strength, therefore, it continues to be essential to increase the strength of the joint structure in the brazed portions of fins.